To improve fuel economy, hybrid electric vehicles (HEVs) may utilize regenerative (regen) braking, in which kinetic energy is converted by an electric machine into storable energy during braking and then made available for vehicle propulsion. During a wheel slip event (e.g., an ABS event), regenerative braking may be removed. The transition from regenerative braking to friction braking may be abrupt and may result in a temporary reduction in overall braking torque as the regenerative braking is removed and the friction braking is applied. If the ABS event occurs on a surface with a low friction coefficient, a faster rate of regenerative braking reduction may be advantageous since it may minimize wheel lockup. However, if the slip event occurs on a surface with a high friction coefficient, fast regenerative braking reduction may not necessarily be advantageous. For example, if a wheel slip event occurs during a CMbB (Collision Mitigation by Brakes) event, especially at higher decelerations, it may not be necessary to reduce regenerative braking fast or even at all since such reduction may result in a 100-200 ms delay in overall braking torque generation.
Accordingly, a system and method for controlling regenerative braking to prevent or minimize reduction of overall braking torque during wheel slip events is needed.